I grow incarnata in a large pot. My passies don't like the acidic clay soil we have in our yard, but in a pot it does just fine. I use a pot with lots of drainage holes (sometimes I drill extra ones) and use a lot perlite or something mixed in with your regular potting soil for good drainage to prevent root rotting. I started mine from seed early this spring and it is now about tall as me (5'6"). It hasn't taken anything over but its own trellis so far :) I suppose it could still spread by seeds later though.

You may need to protect the pot in your zone in the winter because things don't seem as hardy in pots as in the ground.
Maybe someone from a zn 6 could comment more on that.
~SJN

I have done it successfully. I started mine in the ground first, however, dug them up & put them in pots. Use a deep pot, as vines do not like shallow ones.